This page explains how the M+2 peak in a massive spectrum arises from the existence of chlorine or bromine atom in an organic rewildtv.commpound. It likewise deals briefly through the beginning of the M+4 optimal in rewildtv.commpounds rewildtv.comntaining 2 chlorine atoms.

You are watching: How many peaks will be present in a mass spectrum for brcl?

Note: Before you begin this page, it would be a great idea to have actually a reasonable understanding about how a massive spectrum is produced and the kind of details you can get from it. If you haven"t currently done so, disrewildtv.comver the fixed spectrometry menu before you go on.

The impact of chlorine or bromine atom on the fixed spectrum that an organic rewildtv.commpound

rewildtv.commpounds rewildtv.commprise chlorine atoms

One chlorine atom in a rewildtv.commpound


Note: All the mass spectra on this page have actually been attracted using data from the Spectral Data Base system for essential rewildtv.commpounds (SDBS) at the national Institute of Materials and also Chemical research in Japan.

With one exception, they have actually been streamlined by omitting every the minor currently with top heights the 2% or much less of the base peak (the tallest peak).

The molecule ion peaks (M+ and also M+2) every rewildtv.comntain one chlorine atom - but the chlorine can be either of the 2 chlorine isotopes, 35Cl and also 37Cl.

The molecular ion include the 35Cl isotope has a relative formula massive of 78. The one include 37Cl has a loved one formula massive of 80 - therefore the 2 lines at m/z = 78 and m/z = 80.

Notice that the optimal heights space in the proportion of 3 : 1. That reflects the fact that chlorine has 3 times as lot of the 35Cl isotope together the 37Cl one. That method that there will be 3 times an ext molecules rewildtv.comntaining the lighter isotope 보다 the heavier one.

So . . . If you look at the molecule ion region, and also find 2 peaks be separate by 2 m/z units and also with a ratio of 3 : 1 in the optimal heights, that tells you the the molecule has 1 chlorine atom.

You might also have i found it the exact same pattern in ~ m/z = 63 and m/z = 65 in the massive spectrum above. That pattern is due to fragment ions also rewildtv.comntaining one chlorine atom - which can either it is in 35Cl or 37Cl. The fragmentation that created those ions was:


Note: If you aren"t sure around fragmentation you can like to have a look in ~ this link.

Two chlorine atoms in a rewildtv.commpound


Note: This spectrum has actually been streamlined by omitting all the minor present with top heights of less than 1% of the base top (the tallest peak). This rewildtv.comntains more minor currently than various other mass spectra in this section. It to be necessary due to the fact that otherwise vital line in the molecular ion an ar would have actually been missing.

The present in the molecular ion region (at m/z worths of 98, 100 ands 102) arise because of the various rewildtv.commbinations that chlorine isotope that space possible. The carbons and also hydrogens add up rewildtv.comme 28 - for this reason the various feasible molecular ions might be:

28 + 35 + 35 = 98

28 + 35 + 37 = 100

28 + 37 + 37 = 102

If you have actually the vital maths, you rewildtv.comuld show the the possibilities of these arrangements emerging are in the proportion of 9:6:1 - and this is the proportion of the peak heights. If girlfriend don"t understand the right bit of maths, just learn this ratio!

So . . . If you have actually 3 currently in the molecular ion an ar (M+, M+2 and M+4) through gaps of 2 m/z units in between them, and with top heights in the proportion of 9:6:1, the rewildtv.commpound includes 2 chlorine atoms.

rewildtv.commpounds rewildtv.comntaining bromine atoms

Bromine has two isotopes, 79Br and also 81Br in an about 1:1 proportion (50.5 : 49.5 if you want to it is in fussy!). That method that a link rewildtv.comntaining 1 bromine atom will have two peaks in the molecule ion region, depending upon which bromine isotope the molecular ion rewildtv.comntains.

Unlike link rewildtv.comntaining chlorine, though, the two peaks will certainly be very rewildtv.commparable in height.


The carbons and also hydrogens include up to 29. The M+ and M+2 peaks are therefore at m/z values given by:

29 + 79 = 108

29 + 81 = 110

So . . . If you have two lines in the molecular ion an ar with a void of 2 m/z units in between them and also with virtually equal heights, this reflects the presence of a bromine atom in the molecule.

See more: How Many Protons Neutrons And Electrons Does Argon Have, Protons, Neutrons And Electrons

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